A four-and-a-half minute silence was held at the spot where Michael Brown was killed. Credit: Reuters

Hundreds of people have gathered in Ferguson, USA, to mark one year since unarmed black teenager Michael Brown was shot dead by a white police officer.

A four-and-a-half minute silence was held at the spot where he was killed to represent the roughly four-and-a-half hours the 18 year old's body lay in the street after being shot.

The crowd, which included his father Michael Brown Snr, then took part in a silent march in memory of the teen and others killed by police.

At the memorial, Brown's father wore a T-shirt bearing his son's image and the slogan "Chosen for Change." Others held "Black Lives Matter" banners and signs calling for justice for those killed by police.

Brown's death sparked months of protests in America, including incidents of rioting and arson.

Brown's death sparked months of protests, including incidents of rioting and arson. Credit: Reuters

The police officer who shot and killed an unarmed black teenager in Ferguson, Missouri, did not get a severance deal when he resigned, the mayor has confirmed.

Darren Wilson handed in his notice after days of protests in the town following a grand jury's decision not to indict him for the shooting, saying he feared for his own safety and that of his fellow officers.

Ferguson Mayor James Knowles confirmed Wilson would get "no severance or extension of benefits" after his resignation.

The police officer Darren Wilson who killed Michael Brown has resigned from the Ferguson Police Department, his attorney said, according to Associated Press.

The news agency reported the decision, which comes nearly four months after the fatal confrontation with the black 18-year-old that fueled protests in the St. Louis suburb and across the nation.

Darren Wilson, 28, has been on administrative leave since the shooting on Aug. 9. His resignation was announced Saturday by one of his attorneys, Neil Bruntrager. AP reported Mr Bruntrager as saying the resignation is effective immediately.

A policeman and member of the National Guard detain a man who was demanding justice for the killing of Michael Brown. Credit: Reuters

Fifteen people were arrested overnight in Ferguson after taking part in protests against a decision not to indict the white police officer who killed an unarmed black teenager.

Tensions escalated after police said protesters began illegally blocking an avenue.

A group of around 100 protesters had marched down the avenue towards the city's police and fire departments chanting, blocking traffic and stopping in front of businesses. One protester said:

I served my country. I spent four years in the Army, and I feel like that's not what I served my country for. I served my country for justice for everyone. Not because of what colour, what age, what gender or anything.